We developed an application which is rendering multiple video streams via DirectShow, thereby including our own renderering filter, source and decoding filters are also our own make and worked good and performant so far. The renderer is D3D9Ex based and
running with FlipEx presentation mode. Each of the videos we render runs its own set of worker threads and of course its own renderer sink.

Single HD monitor attached

When setting up a test scenario rendering 20 SD MPEG-4 sources evenly distributed on the LTSB W10 appliance, GPU load is around 70%-75%. The CPU load is also evenly distributed in good shape across all cores.
When testing the same scenario on the CBB W10 appliance, GPU load already climbs up to 100% when adding the 7th video to the test scenario, but I can still add up to 20 videos, as planned for the test without any significant degradition in terms of video smoothness.

Two HD monitors attached (extending the display to 3840*1200 pixel)

When I add a second HD monitor to the system, the GPU load in the CBB system starts to climb up to 100% similar to the above test scenario. If we look at the number of smooth playing videos, the CBB setup now exposes more hickups and frame drops, as on the
LTSP setup.

Conclusion

Microsoft introduced changes into the W10 CBB 1607 version, which seems either to disturb the GPU load measurement or degrades the rendering performance on bigger surfaces or both.
Note: All Power and GPU settings, where perfomance has a tradeoff against quality or power savings are selected to prefer performance. Also visual effects are adjusted for best performance.

Question

What did Microsoft change between W10 IoT LTSB 1511 and W10 IoT CBB 1607, to influence graphics performance, and how can I eventually get hold of these change(s) to bring back the CBB situation to normal (a.k.a. LTSB)?

P.S.: When displaying 6 videos only, the LTSB setup shows a steady low GPU load at 18%, whereas the CBB setup shows lots of spikes, thereby the GPU load peaking up to 100% shortly. I will add these pictures, as soon as my account has been checked.